Parkinson's disease (PD) has long been characterized as a classic motor disorder arising from the death of dopamine-producing neurons in the substantia nigra of the midbrain. In addition to the motor symptoms, a variety of non-motor symptoms also manifest during the course of PD. Perhaps because the motor symptoms often are alleviated by dopaminergic medications, whereas the non-motor symptoms are not reliably improved, researchers and clinicians have focused on the motor symptoms and failed to consider the often-devastating effects of the non-motor symptoms. Of these non-motor symptoms, anxiety occurs in up to 40% of PD patients and significantly contributes to poorer quality of life, often to a greater extent than do the motor symptoms. The pathophysiology of anxiety in PD remains poorly understood, even in regards to whether anxiety in these patients is a secondary symptom in reaction to the motor symptoms, or a primary symptom of the disease related to underlying neuropathology. In a departure from the traditional belief of the source of the disease as being in the midbrain, a current view is that PD brain pathology begins in the lower brainstem before progressing to the midbrain and neocortex. If anxiety in PD develops prior to the motor symptoms, it may be a marker of underlying neuropathology in the brainstem and then limbic regions during the prodromal stages of the disease. The goals of the study are to assess the nature of anxiety in PD and examine the relationship between anxiety and cognition in this population (Aim 1) and to assess the utility and feasibility of a cognitive-behavioral intervention for anxiety in PD (Aim 2). Aim 1 will examine anxiety in PD using semi-structured diagnostic interviews, self-report questionnaires, and neuropsychological measures. It is expected that anxious PD patients will present mainly with generalized anxiety disorder, social anxiety disorder, or panic disorder and that the anxiety symptoms will not be solely a reaction to the motor symptoms of PD. The main hypothesis for this aim is that PD patients who perform poorer on cognitive tests will show more anxiety than those with better cognitive skills as cognitive impairments are indicative of more advanced PD neuropathology, implicating both brainstem (anxiety) and neocortex (cognition); pre-existing anxiety may also interfere with patients' ability to perform optimally on cognitive tests. Aim 2 will assess the utility and feasiblity of cognitive- behavioral intervention for anxiety in PD patients, using a single-case experimental design. It is predicted that the intervention will reduce anxiety and PD-specific symptoms, namely freezing and tremor, which may be exacerbated by anxiety. The results of the study will facilitate a better understanding of anxiety in PD and inform future treatment development. Because many PD patients do not respond well to pharmacotherapy for anxiety, this project addresses a critical public health need in its examination of a psychological intervention to manage anxiety in PD patients and ultimately optimize their quality of life.